[Closed] friday physics question

Yes. If you use a heat pump.

pop that on the stove and find out
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depends on the shape of the heat source

No.

not even with a heat pump.

No - as energy cannot be created or destroyed. It can only change form

So for the item being heated, if it were to get hotter than the item doing the heating then energy would have to be created somewhere - unless you were some kind of freeride scientist and you're talking about converting kinetic downhill energy into brake rotor heat where the rotor gets hotter than the brakes

if it were to get hotter than the item doing the heating then energy would have to be created somewhere

Peltier heat pump - the heat source is just the air, but turn it on and one side gets hot enough to boil water.

No.

not even with a heat pump.

So an air sourced heat pump will never warm your house warmer than the outside temperature?
That's a great idea.

I thought air heaters used the friction of the air over something rather than the temperature of the air.

NOpe I am wrong it is basically the outside is massive and has loads of heat energy as it is above absolute zero

Two things going on in this thread.

1. People talking about heat pumps which [i]do work[/i] to shift energy from a large body at low temperature to a smaller body at higher temperature. No laws are violated.

2. People talking about a situation where you're heating say, a pot on the stove. In this case the bot cannot become hotter than the flame.

Yes.

Pop-Tarts.

Yes. A microwave oven makes things hotter that the heat source. The Microwave source are pretty cool (temperature wise). One of the fundamental thermodynamic laws is energy can be transferred from an object to a colder or hotter, so you can make a hotter object hotter and a colder object cooler. Obviously one way will gapped naturally via conduction and convection and the other will need some intervention, like you need a fridge/freezer to transfer energy from a cold object to make it cooler.

Also what about a nuclear fission reaction where you pack the fuel rods closely together and the temperature rises to very high temperatures due to the radiation being emitted starting a chain reaction.

(P1 x V1)/T1 = (P2 x V2)/T2

In other words, change the volume and/or pressure and the temperature will change. Boyles and Charles' Laws

[quote=bearnecessities said]Yes.
Pop-Tarts.

Finally we get a scientist

Yes.

Pop-Tarts.

Yep, that's a whole physics and chemistry enigma right there

Thermite ?

I see your pop tarts and raise you a McDonald's apple wrap

Depends on how you are heating, as mentioned. There are many ways to transfer energy, and this energy can change form in the process.

Surely it depends on whether the heating results in a chemical reaction within the thing/substance being heated. One example being magnesium: I believe this will burn at a temperature of up to 3100 deg C, with an ignition point at 473 deg C.

I might be wrong, though.

exothermic reactions - eg pot noodle / cuppa soup 🙂

Cups of tea from those roadside "butty vans", particularly that one just off the east side of the A34 in Brum.

More details please Yunki but if we are talking plain and simple conduction then no.

http://www.ior.org.uk/ior_/fantastic_fridges_site/science/how%20your%20fridge%20works.htm

Bicycle pump. See Boyle's law above.

What do you mean by "hot"? A bath has a lot of heat but a relatively low temperature, a match is high temperature but not much heat.

Flanders & Swann - 'First And Second Law':

Hmm wait.. Liquid helium and quantum superfluids..

My memory of the law is

"heat cannot of itself pass from a hot body to a hotter body"

So the microwaves aren't heat so that doesn't brake the law

Chemical reactions generate heat. But its not really transferring heat of its self

We can make heat by doing work, hence the bicycle pump

Heat pumps move heat from one place to another. But again the energy transferred is not in the form of heat. It requires work to be done

I'v had to google Peltier coolers but it looks like the energy is transferred electrically

So I think the answer is no. But it does really depend on what the OP intended

Oh and that the Op meant hotter as in higher temperature

crankboy - Member
Flanders & Swann

My induction hob boils water in a pan very quickly, but stays relatively cool.

My induction hob boils water in a pan very quickly, but stays relatively cool.

But the heat source is the metal of the pan. The hob is a coil with an alternating current that induces a huge current in the ferrous pan and generates heat in the material of the pan.

A microwave does similar but generates heat (through dipoles) in the water itself as the frequency is tuned for water in food.